A turbocharger may be provided in an engine to improve engine torque or power output density. The turbocharger may include an exhaust driven turbine coupled to a compressor via a drive shaft. The compressor may be fluidly coupled to an air intake manifold in the engine connected to a plurality of engine cylinders. Exhaust flow from one or more engine cylinders may be directed to a turbine wheel causing the turbine to rotate about a fixed axis. The rotational motion of the turbine drives the compressor which compresses air into the air intake manifold to increase boost pressure based on engine operating conditions.
The compressor may include a sleeve having a plurality of sleeve slots, which may be selectively aligned with either a bleed slot or recirculation slot on a casing shroud coupled to the sleeve to control air flow conditions in the compressor based on turbocharger and/or engine operating conditions. In this way, the position of the sleeve may be selectively adjusted relative to the casing shroud to address choke or surge conditions. However, adjusting the position of the sleeve along the casing shroud to align the sleeve slots with either the choke or surge slots or to block both the choke and surge slots during engine operation may pose challenges and may lead to flow leakage or affect compressor performance. For example, misalignment of the sleeve slots relative to either the choke or surge slots may occur when the sleeve is improperly adjusted relative to the casing shroud, thereby creating openings in the compressor that may allow air leakage. Increased air flow leakage in the compressor system may decrease compressor efficiency. Further, the sleeve may bind to the casing treatment when actuated, which may create difficulty when adjusting compressor flow geometry.
One example approach for addressing the above problems in a turbocharger compressor is shown by Sun in U.S. patent number 2014/0377051. Therein, a system is disclosed that includes a turbocharger compressor having an actuatable annular disk comprising a first group of choke slots, an outer annular disk comprising a second group of choke slots, and an actuator to rotate the actuatable annular disk relative to the outer annular disk to vary alignment of the choke slots on both disks. The compressor further includes a bleed port that is fluidly coupled to a compressor inlet and is continuously open during engine operation.
However, the inventors herein have recognized potential issues with such a system. As one example, due to the complex nature of the system, misalignment of the actuatable and outer annular disks may occur when the actuatable disk is adjusted from one position relative to the outer disk to another position. In this case, misalignment of the actuatable and outer annular disks may cause flow leakage in the casing shroud which may affect the performance of the compressor. In another example, since the surge slot is always open during engine operation, air may be continuously recirculated from the compressor wheel back to the compressor inlet. Continuous recirculation of air in the turbocharger compressor may not be always necessary, especially when compressor conditions or engine operating conditions do not warrant constant air flow recirculation.
In one example, the issues described above may be addressed by an actuator assembly for a slidable sleeve of a turbocharger compressor, comprising: a fork arm coupled to the slidable sleeve; a rotatable lever arm coupled to the fork arm via a rigid connecting shaft; a connector rod coupled between the lever arm and a rotatable element; and an actuator unit coupled to the rotatable element and attached to an attachment case, the attachment case coupled to the turbocharger compressor. In this way, an engine controller may control the actuator assembly to move the slidable sleeve to a position along a casing treatment, thereby adjusting the alignment of sleeve slots on the slidable sleeve relative to choke or surge slots on the casing treatment to accommodate a wide range of airflow conditions while increasing compressor efficiency.
For example, the actuator unit of the actuator may receive a signal from the controller and then the actuator actuates the rotatable element which moves the connector rod coupled to the rotatable lever arm. The motion of the connector rod rotates the lever arm which in turn moves the fork arm and slidable sleeve along the casing treatment to vary alignment of sleeve slots on the slidable sleeve relative to choke and surge slots on the casing treatment.
In another example, an engine controller may control the actuator to move the slidable sleeve to a position relative to the casing treatment where the sleeve slots are aligned with choke slots (e.g., chokes slots are open) on the casing treatment and not aligned with the surge slots (e.g., surge slots are closed) on the casing treatment. In this case, air may be delivered to a compressor wheel in the casing treatment via the choke slots, thereby extending choke flow capacity. In another example, the slidable sleeve may be moved to a position relative the casing treatment where the sleeve slots are not aligned with either choke slots (e.g., chokes slots are closed) and aligned with the surge slots (e.g., surge slots are open). In this case, air entering the compressor may be recirculated via the surge slots to extend the surge margin.
The actuator assembly coupled to the slidable of the compressor may confer several advantages. For example, movement of the rotatable element, connector rod and lever arm allow the fork arm and slidable sleeve to slide along the casing treatment (to vary alignment of the sleeve slots relative to the choke and surge slots) without taking up much space and/or fits within a space allowed by a geometry of the compressor (e.g., adjacent to the volute of the compressor). In this case, the actuator assembly provides for a more compact system that varies compressor flow geometry to accommodate a wide range of flow conditions. Further, the fork arm and slidable sleeve may move only in an axial direction parallel to the inlet air flow and a rotational axis of the compressor. In this way, the actuator assembly may be configured to move the slidable sleeve quickly to meet engine requirements with minimal torque requirement, while reducing the cost of the actuator.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.